Spark plug



M. PERELES March 2, 1948.

SPARK PLUG Filed April 10, 1943 INVENTOR. MAURICE PEREL 5 A T TORNE VS Patented Mar. 2, 1948 UNITED STATES PATENT OFFICE SPARK PLUG Maurice Pereles, East Orange, N. J.

Application April 10, 1943, Serial No. 482,551

2 Claims. (01. 123-169) This invention relates to improvements in spark plugs and has for an object the provision of a spark plug of the ceramic type in which the heat transfer between the center or live electrode and the ceramic is greatly increased over that of ex isting plugs. In my new and improved spark plug, I increase the surface contact between the metal of the electrode and the ceramic by forming on the electrode a continuous series of grooves and thereby increase the length of its surface in the neighborhood of threefold. I may also increase the surface area by knurling the same with either criss-cross knurling or by straight knurls.

Another object of the invention is the provision of a spark plug in which the seal between the ceramic and the metal portion of the shell thereabout is effected by shrinking the metal onto the ceramic.

A. further object of the invention is the prc= vision of a shielded or well type spark plug in which the chances of flashing over between the electrode and the shell, via the thin wall of insulation is minimized. This is accomplished by forming that portion of the ceramic insulator, above the electrode, solid and thereafter drilling the well into the ceramic and clown to the electrode after the ceramic has been assembled into the shell.

Other objects and advantages of the invention will be apparent to those skilled in the art upon a study of this specification and the accompanying drawings, in which- Figure is a sectional elevation of the core, the electrode having been molded into the ceramic;

Figure 2 is a sectional elevation of the upper portion of the shell;

Figure 3 is a sectional elevation of the shell of Figure 2 with the core shown in Figure l in assembled relation;

Figure 4 is a cross sectional elevation of the assemhly oi Figure 3 after it has been combined with the lower portion of the shell carrying the ground electrode;

Figure 5 is an enlarged fragmentary section of the lower portion of the plug shown in Figure;

Figure El is a sectional elevation of a modified form of the invention as applied to an open type spark plug; and

Figure 7 is a sectional elevation of a spark plug of the shielded type having a one piece shell.

The live electrode I!) has a sparking end H, which may be made in any desired shape, a shank I2, and a. contact head I 3, adapted to receive current from a source of high tension current. The shank l2, as may clearly be seen in Figure 5,

' is provided with a series of grooves M which provide reater surface area in contact with the ceramic insulator.

I contemplate molding the ceramic around the electrode to, and may provide the electrode with a shank 16 (shown in dot-dash lines) for positively locating the electrode in the mold.

In molding the electrode into the ceramic, I prefer to use a vitreous material containing mica or micaceous minerals which are in a finely divideo state throughout the ceramic. Such ceramics are disclosed in U. S. Patent No. 394,973, dated October 25, 1921. I do not limit myself to the exact ceramic or process of making the same, but merely give this by way of example.

A suitable mold having been formed, the elec trode is positioned in the mold and is helcl in axial alignment with the bore of said mold by means of the locating shank l8 shove referred to.

The ceramic it has a straight cylindrical wall,

which may terminate in a shoulder El, and a tapered surface it thereof extends from the shoultier H to the electrode end H. The shoulder ll may serve for locating the ceramic in the shell, as will presently be described. After the ceramicelectrode assembly is taken from the mold, the locating shank it may then he machined off.

In Figure 2 is shown the upper portion of a twopart shell for a shielded type aircraft spark plug.

It consists of a body portion l9 which includes a threaded portion 20 near the upper end; thereof to be engaged by a threaded nut connected to the shielding on the spark plug cahle (not shown). The body portion is also includes a hexagonal portion 2t, and a second threaded Portion it which threadedly engages the lower portion oi the shell, to he presently described.

The bore 23 in the body i9 is so proportioned to the diameter of the ceramic it that the two members may he assembled with a shrink fit suitable for eitemng a fluid tight seal between the ceramic l 5 and the body it. I preheat the hotly l3 and, with the molded insulator room temperature. the hotly it is uickly pushed on the straight shank of the insulatorlfi until the bottom of the threaded end 22 comes to rest against the shoulder El. .Then the assembly is allowed to cool down to room temperature.

The assembly may then be placed in the .lig and ahole Z4 is drilled in the insulator down to and uncovering the head I: of the electrode l0.

. At this stage, the assembly has the. appearance wall l 0! the insulator, particularly in the neighborhood of the head 18, and thereby eliminate chances of the spark Jumping trom the head I3 via such cracks into the interior wall 29 ,0! the body 19.

The lower portion of the shell consists of a body 25 having an upper hexagonal portion 36 and a bore2'l extending therethrough. The upper portion of the bore 21 is threaded, and a recess 28 at the upper end thereof is adapted to receive a sealing gasket 29, which gasket lies between the shoulder 30, formed on the body 19, so that when the threaded portion 22 of the body I9 is screwed into the shell 25, a fluid tight seal is efiected between the body 19 and the body 25.

The body 25 is provided with threads 91 which engage a threaded hole in the cylinder head of the engine. A ground electrode 92 is secured in the lower end of the body 25, and when the spark plug is assembled, the sparking end it of the electrode I0 is in concentric relation to the ground electrode 32 with the proper sparking gap therebetween.

The ground electrode may be spun in, in the usual manner, which consists of counterboring the lower end of the shell, in the manner shown at 33 in Figure 7, leaving a thin annular wall 34 thereabout. Then the ground electrode 82 is positioned in the counterbored portion 33 and up against the shoulder 35. Then the thin annular wall 34 is spun or curled over, such as is shown at 34"- in Figure 4.

In the modification shown in Figure 6, which is for an open type spark plug, the electrode 80 has a sparking end H and a grooved shank 12 similar to the corresponding parts described in connection with the electrode ill. The upper end of the electrode however, is modified as follows: Above the head 13 is provided a thread-- ed shank 36 which carries a lock washer 31 against which a nut 38 bears. The threaded shank 36 may also carry a suitable nut or fitting 39 adapted to be engaged by a clip or terminal on the ignition cable. 1

The body I9"- is foreshortened and has a hexagonal portion 2 l and a lower threaded portion 22*- which engages the threads ln the upper portion of the bore 21 in the shell member 25. Sealing between the members 13 and 25 is likewise effected by means of a gasket 29.

In the modification shown in Figure 7, the shell 40 is formed of one piece of material. It includes a straight shank portion 40, an upper threaded portion 20, a lower threaded portion 3 I adapted to engage a threaded hole in the engine cylinder, and a hexagonal portion 26 to be engaged by a suitable wrench for applying the plug to or removing the plug from the engine. A bore 23 formed therein has an enlarged portion 21 iormed therebetween a shoulder M which forms a stop to ,be engaged by the shoulder ll on the insulatorwhen the insulator is assembled in the shell.

In assembling the insulator in the shell, the shell may be pre-heated, and with the insulator at room temperature the shell is applied thereto, as described above in connection with Figures 1, 2 and 3.

Since the insulator enters the shell from the lower or firing end, the ground electrode 32 is- 0 omitted until after the insulator has been assembled lnto the shell. Then the ground electrode is pressed into the counterbored recess 93 against the shoulder 35, and the annular rim 23 is spun over to retain the ground electrode in position therein. The well 29 is drilled in the same manner as described above in connection with Figure 3.

Although I have herein described a spark plug and .the method of making the same and two modifications thereof, it is obvious that other types of spark plugs may be made in the manner herein described, and changes may be made in the order of the steps taken in carrying out the invention, without departing from the spirit I thereof as set forth in the following claims.

- What is claimed is:

1. In a spark plug an electrode having a spark-- ing tip, a contact head, and a portion of reduced diameter therebetween, said portion having been serrated to increase itsnormal surface, and a ceramic body molded on to said electrode and including an annular portion integral therewith and extending beyond said head.

2. In a spark plug a one piece electrode having -a sparking tip, a contact head and a portion therebetween of reduced diameter threaded or serratedto increase its surface, a ceramic molded on to said electrode and extending from said sparking tip to a point beyond said contact head, the portion of said ceramic beyond said head being solid, said ceramic intimately contacting said threaded or serrated portion, thereby providing maximum heat transfer relation between said ceramic and said portion, a shell assembled on to said ceramic, and a well formed in said solid portion of said ceramic after assembly, said well extending down to and uncovering said head.

MAURICE PERELES.

REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,214,472 Jeffery Jan. 30, 1917 1,331,091 Becker Feb. 17, 1920 1,360,814 Storms Nov. 30, 1920 1,494,099 Cole May 13, 1924 I 1,525,453 Littleton Feb. 10, 1925 1,564,981 Smith Dec. 8, 1925 1,635,186 Littleton -11.. July 12, 1927 1,708,634 Rees Apr. 9, 1929 1,837,723 McGraw Dec. 22, 1931 1,837,754 Calmus et a1 Dec. 22, 1931 1,843,045 Schupp Jan. 26, 1932 1,940,324 Rabezzanag Dec. 19, 1933 2,020,966 Rohde Nov. 12, 1935 2,178,774 Bogoslowsky Nov. 7, 1939 2,223,013 De Chard Nov. 26, 1940 2,238,397 Rabezzana Apr. 15, 1941 2,254,082 Meyer Aug. 26, 1941 2,272,210 King Feb. 10, 1942 2,355,443 Jeffery Aug. 8, 1944 FOREIGN PATENTS Number Country Date Germany July 21, 1921 

